1 /* 2 * GPIO based serio bus driver for bit banging the PS/2 protocol 3 * 4 * Author: Danilo Krummrich <danilokrummrich@dk-develop.de> 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License version 2 as 8 * published by the Free Software Foundation. 9 */ 10 11 #include <linux/gpio/consumer.h> 12 #include <linux/interrupt.h> 13 #include <linux/module.h> 14 #include <linux/serio.h> 15 #include <linux/slab.h> 16 #include <linux/platform_device.h> 17 #include <linux/workqueue.h> 18 #include <linux/completion.h> 19 #include <linux/mutex.h> 20 #include <linux/preempt.h> 21 #include <linux/property.h> 22 #include <linux/of.h> 23 #include <linux/jiffies.h> 24 #include <linux/delay.h> 25 26 #define DRIVER_NAME "ps2-gpio" 27 28 #define PS2_MODE_RX 0 29 #define PS2_MODE_TX 1 30 31 #define PS2_START_BIT 0 32 #define PS2_DATA_BIT0 1 33 #define PS2_DATA_BIT1 2 34 #define PS2_DATA_BIT2 3 35 #define PS2_DATA_BIT3 4 36 #define PS2_DATA_BIT4 5 37 #define PS2_DATA_BIT5 6 38 #define PS2_DATA_BIT6 7 39 #define PS2_DATA_BIT7 8 40 #define PS2_PARITY_BIT 9 41 #define PS2_STOP_BIT 10 42 #define PS2_TX_TIMEOUT 11 43 #define PS2_ACK_BIT 12 44 45 #define PS2_DEV_RET_ACK 0xfa 46 #define PS2_DEV_RET_NACK 0xfe 47 48 #define PS2_CMD_RESEND 0xfe 49 50 struct ps2_gpio_data { 51 struct device *dev; 52 struct serio *serio; 53 unsigned char mode; 54 struct gpio_desc *gpio_clk; 55 struct gpio_desc *gpio_data; 56 bool write_enable; 57 int irq; 58 unsigned char rx_cnt; 59 unsigned char rx_byte; 60 unsigned char tx_cnt; 61 unsigned char tx_byte; 62 struct completion tx_done; 63 struct mutex tx_mutex; 64 struct delayed_work tx_work; 65 }; 66 67 static int ps2_gpio_open(struct serio *serio) 68 { 69 struct ps2_gpio_data *drvdata = serio->port_data; 70 71 enable_irq(drvdata->irq); 72 return 0; 73 } 74 75 static void ps2_gpio_close(struct serio *serio) 76 { 77 struct ps2_gpio_data *drvdata = serio->port_data; 78 79 disable_irq(drvdata->irq); 80 } 81 82 static int __ps2_gpio_write(struct serio *serio, unsigned char val) 83 { 84 struct ps2_gpio_data *drvdata = serio->port_data; 85 86 disable_irq_nosync(drvdata->irq); 87 gpiod_direction_output(drvdata->gpio_clk, 0); 88 89 drvdata->mode = PS2_MODE_TX; 90 drvdata->tx_byte = val; 91 92 schedule_delayed_work(&drvdata->tx_work, usecs_to_jiffies(200)); 93 94 return 0; 95 } 96 97 static int ps2_gpio_write(struct serio *serio, unsigned char val) 98 { 99 struct ps2_gpio_data *drvdata = serio->port_data; 100 int ret = 0; 101 102 if (in_task()) { 103 mutex_lock(&drvdata->tx_mutex); 104 __ps2_gpio_write(serio, val); 105 if (!wait_for_completion_timeout(&drvdata->tx_done, 106 msecs_to_jiffies(10000))) 107 ret = SERIO_TIMEOUT; 108 mutex_unlock(&drvdata->tx_mutex); 109 } else { 110 __ps2_gpio_write(serio, val); 111 } 112 113 return ret; 114 } 115 116 static void ps2_gpio_tx_work_fn(struct work_struct *work) 117 { 118 struct delayed_work *dwork = to_delayed_work(work); 119 struct ps2_gpio_data *drvdata = container_of(dwork, 120 struct ps2_gpio_data, 121 tx_work); 122 123 enable_irq(drvdata->irq); 124 gpiod_direction_output(drvdata->gpio_data, 0); 125 gpiod_direction_input(drvdata->gpio_clk); 126 } 127 128 static irqreturn_t ps2_gpio_irq_rx(struct ps2_gpio_data *drvdata) 129 { 130 unsigned char byte, cnt; 131 int data; 132 int rxflags = 0; 133 static unsigned long old_jiffies; 134 135 byte = drvdata->rx_byte; 136 cnt = drvdata->rx_cnt; 137 138 if (old_jiffies == 0) 139 old_jiffies = jiffies; 140 141 if ((jiffies - old_jiffies) > usecs_to_jiffies(100)) { 142 dev_err(drvdata->dev, 143 "RX: timeout, probably we missed an interrupt\n"); 144 goto err; 145 } 146 old_jiffies = jiffies; 147 148 data = gpiod_get_value(drvdata->gpio_data); 149 if (unlikely(data < 0)) { 150 dev_err(drvdata->dev, "RX: failed to get data gpio val: %d\n", 151 data); 152 goto err; 153 } 154 155 switch (cnt) { 156 case PS2_START_BIT: 157 /* start bit should be low */ 158 if (unlikely(data)) { 159 dev_err(drvdata->dev, "RX: start bit should be low\n"); 160 goto err; 161 } 162 break; 163 case PS2_DATA_BIT0: 164 case PS2_DATA_BIT1: 165 case PS2_DATA_BIT2: 166 case PS2_DATA_BIT3: 167 case PS2_DATA_BIT4: 168 case PS2_DATA_BIT5: 169 case PS2_DATA_BIT6: 170 case PS2_DATA_BIT7: 171 /* processing data bits */ 172 if (data) 173 byte |= (data << (cnt - 1)); 174 break; 175 case PS2_PARITY_BIT: 176 /* check odd parity */ 177 if (!((hweight8(byte) & 1) ^ data)) { 178 rxflags |= SERIO_PARITY; 179 dev_warn(drvdata->dev, "RX: parity error\n"); 180 if (!drvdata->write_enable) 181 goto err; 182 } 183 184 /* Do not send spurious ACK's and NACK's when write fn is 185 * not provided. 186 */ 187 if (!drvdata->write_enable) { 188 if (byte == PS2_DEV_RET_NACK) 189 goto err; 190 else if (byte == PS2_DEV_RET_ACK) 191 break; 192 } 193 194 /* Let's send the data without waiting for the stop bit to be 195 * sent. It may happen that we miss the stop bit. When this 196 * happens we have no way to recover from this, certainly 197 * missing the parity bit would be recognized when processing 198 * the stop bit. When missing both, data is lost. 199 */ 200 serio_interrupt(drvdata->serio, byte, rxflags); 201 dev_dbg(drvdata->dev, "RX: sending byte 0x%x\n", byte); 202 break; 203 case PS2_STOP_BIT: 204 /* stop bit should be high */ 205 if (unlikely(!data)) { 206 dev_err(drvdata->dev, "RX: stop bit should be high\n"); 207 goto err; 208 } 209 cnt = byte = 0; 210 old_jiffies = 0; 211 goto end; /* success */ 212 default: 213 dev_err(drvdata->dev, "RX: got out of sync with the device\n"); 214 goto err; 215 } 216 217 cnt++; 218 goto end; /* success */ 219 220 err: 221 cnt = byte = 0; 222 old_jiffies = 0; 223 __ps2_gpio_write(drvdata->serio, PS2_CMD_RESEND); 224 end: 225 drvdata->rx_cnt = cnt; 226 drvdata->rx_byte = byte; 227 return IRQ_HANDLED; 228 } 229 230 static irqreturn_t ps2_gpio_irq_tx(struct ps2_gpio_data *drvdata) 231 { 232 unsigned char byte, cnt; 233 int data; 234 static unsigned long old_jiffies; 235 236 cnt = drvdata->tx_cnt; 237 byte = drvdata->tx_byte; 238 239 if (old_jiffies == 0) 240 old_jiffies = jiffies; 241 242 if ((jiffies - old_jiffies) > usecs_to_jiffies(100)) { 243 dev_err(drvdata->dev, 244 "TX: timeout, probably we missed an interrupt\n"); 245 goto err; 246 } 247 old_jiffies = jiffies; 248 249 switch (cnt) { 250 case PS2_START_BIT: 251 /* should never happen */ 252 dev_err(drvdata->dev, 253 "TX: start bit should have been sent already\n"); 254 goto err; 255 case PS2_DATA_BIT0: 256 case PS2_DATA_BIT1: 257 case PS2_DATA_BIT2: 258 case PS2_DATA_BIT3: 259 case PS2_DATA_BIT4: 260 case PS2_DATA_BIT5: 261 case PS2_DATA_BIT6: 262 case PS2_DATA_BIT7: 263 data = byte & BIT(cnt - 1); 264 gpiod_set_value(drvdata->gpio_data, data); 265 break; 266 case PS2_PARITY_BIT: 267 /* do odd parity */ 268 data = !(hweight8(byte) & 1); 269 gpiod_set_value(drvdata->gpio_data, data); 270 break; 271 case PS2_STOP_BIT: 272 /* release data line to generate stop bit */ 273 gpiod_direction_input(drvdata->gpio_data); 274 break; 275 case PS2_TX_TIMEOUT: 276 /* Devices generate one extra clock pulse before sending the 277 * acknowledgment. 278 */ 279 break; 280 case PS2_ACK_BIT: 281 gpiod_direction_input(drvdata->gpio_data); 282 data = gpiod_get_value(drvdata->gpio_data); 283 if (data) { 284 dev_warn(drvdata->dev, "TX: received NACK, retry\n"); 285 goto err; 286 } 287 288 drvdata->mode = PS2_MODE_RX; 289 complete(&drvdata->tx_done); 290 291 cnt = 1; 292 old_jiffies = 0; 293 goto end; /* success */ 294 default: 295 /* Probably we missed the stop bit. Therefore we release data 296 * line and try again. 297 */ 298 gpiod_direction_input(drvdata->gpio_data); 299 dev_err(drvdata->dev, "TX: got out of sync with the device\n"); 300 goto err; 301 } 302 303 cnt++; 304 goto end; /* success */ 305 306 err: 307 cnt = 1; 308 old_jiffies = 0; 309 gpiod_direction_input(drvdata->gpio_data); 310 __ps2_gpio_write(drvdata->serio, drvdata->tx_byte); 311 end: 312 drvdata->tx_cnt = cnt; 313 return IRQ_HANDLED; 314 } 315 316 static irqreturn_t ps2_gpio_irq(int irq, void *dev_id) 317 { 318 struct ps2_gpio_data *drvdata = dev_id; 319 320 return drvdata->mode ? ps2_gpio_irq_tx(drvdata) : 321 ps2_gpio_irq_rx(drvdata); 322 } 323 324 static int ps2_gpio_get_props(struct device *dev, 325 struct ps2_gpio_data *drvdata) 326 { 327 drvdata->gpio_data = devm_gpiod_get(dev, "data", GPIOD_IN); 328 if (IS_ERR(drvdata->gpio_data)) { 329 dev_err(dev, "failed to request data gpio: %ld", 330 PTR_ERR(drvdata->gpio_data)); 331 return PTR_ERR(drvdata->gpio_data); 332 } 333 334 drvdata->gpio_clk = devm_gpiod_get(dev, "clk", GPIOD_IN); 335 if (IS_ERR(drvdata->gpio_clk)) { 336 dev_err(dev, "failed to request clock gpio: %ld", 337 PTR_ERR(drvdata->gpio_clk)); 338 return PTR_ERR(drvdata->gpio_clk); 339 } 340 341 drvdata->write_enable = device_property_read_bool(dev, 342 "write-enable"); 343 344 return 0; 345 } 346 347 static int ps2_gpio_probe(struct platform_device *pdev) 348 { 349 struct ps2_gpio_data *drvdata; 350 struct serio *serio; 351 struct device *dev = &pdev->dev; 352 int error; 353 354 drvdata = devm_kzalloc(dev, sizeof(struct ps2_gpio_data), GFP_KERNEL); 355 serio = kzalloc(sizeof(struct serio), GFP_KERNEL); 356 if (!drvdata || !serio) { 357 error = -ENOMEM; 358 goto err_free_serio; 359 } 360 361 error = ps2_gpio_get_props(dev, drvdata); 362 if (error) 363 goto err_free_serio; 364 365 if (gpiod_cansleep(drvdata->gpio_data) || 366 gpiod_cansleep(drvdata->gpio_clk)) { 367 dev_err(dev, "GPIO data or clk are connected via slow bus\n"); 368 error = -EINVAL; 369 } 370 371 drvdata->irq = platform_get_irq(pdev, 0); 372 if (drvdata->irq < 0) { 373 dev_err(dev, "failed to get irq from platform resource: %d\n", 374 drvdata->irq); 375 error = drvdata->irq; 376 goto err_free_serio; 377 } 378 379 error = devm_request_irq(dev, drvdata->irq, ps2_gpio_irq, 380 IRQF_NO_THREAD, DRIVER_NAME, drvdata); 381 if (error) { 382 dev_err(dev, "failed to request irq %d: %d\n", 383 drvdata->irq, error); 384 goto err_free_serio; 385 } 386 387 /* Keep irq disabled until serio->open is called. */ 388 disable_irq(drvdata->irq); 389 390 serio->id.type = SERIO_8042; 391 serio->open = ps2_gpio_open; 392 serio->close = ps2_gpio_close; 393 /* Write can be enabled in platform/dt data, but possibly it will not 394 * work because of the tough timings. 395 */ 396 serio->write = drvdata->write_enable ? ps2_gpio_write : NULL; 397 serio->port_data = drvdata; 398 serio->dev.parent = dev; 399 strlcpy(serio->name, dev_name(dev), sizeof(serio->name)); 400 strlcpy(serio->phys, dev_name(dev), sizeof(serio->phys)); 401 402 drvdata->serio = serio; 403 drvdata->dev = dev; 404 drvdata->mode = PS2_MODE_RX; 405 406 /* Tx count always starts at 1, as the start bit is sent implicitly by 407 * host-to-device communication initialization. 408 */ 409 drvdata->tx_cnt = 1; 410 411 INIT_DELAYED_WORK(&drvdata->tx_work, ps2_gpio_tx_work_fn); 412 init_completion(&drvdata->tx_done); 413 mutex_init(&drvdata->tx_mutex); 414 415 serio_register_port(serio); 416 platform_set_drvdata(pdev, drvdata); 417 418 return 0; /* success */ 419 420 err_free_serio: 421 kfree(serio); 422 return error; 423 } 424 425 static int ps2_gpio_remove(struct platform_device *pdev) 426 { 427 struct ps2_gpio_data *drvdata = platform_get_drvdata(pdev); 428 429 serio_unregister_port(drvdata->serio); 430 return 0; 431 } 432 433 #if defined(CONFIG_OF) 434 static const struct of_device_id ps2_gpio_match[] = { 435 { .compatible = "ps2-gpio", }, 436 { }, 437 }; 438 MODULE_DEVICE_TABLE(of, ps2_gpio_match); 439 #endif 440 441 static struct platform_driver ps2_gpio_driver = { 442 .probe = ps2_gpio_probe, 443 .remove = ps2_gpio_remove, 444 .driver = { 445 .name = DRIVER_NAME, 446 .of_match_table = of_match_ptr(ps2_gpio_match), 447 }, 448 }; 449 module_platform_driver(ps2_gpio_driver); 450 451 MODULE_AUTHOR("Danilo Krummrich <danilokrummrich@dk-develop.de>"); 452 MODULE_DESCRIPTION("GPIO PS2 driver"); 453 MODULE_LICENSE("GPL v2"); 454